Adhesive compositions with block copolymer tackifiers

ABSTRACT

Petroleum Resins particularly effective for use as tackifiers for hot melt adhesives and in tackifiers for solvent-based pressure sensitive adhesives are prepared by a process 
     Wherein (1) a C 8  - and/or C 9  aromatic unsaturated hydrocarbon-containing feed (optionally containing up to 18 wt. % or C 4  or C 5  unsaturated aliphatic hydrocarbons) is first polymerized completely and thereafter a C 5  -aliphatic unsaturated hydrocarbon-containing feed is added, polymerization continued and the reactor effluent stripped to obtain the resin. The order of polymerization may be reversed.

This is a division of application Ser. No. 799,520, filed Nov. 19, 1985, now U.S. Pat. No. 4,757,114.

This invention relates to a process for preparing petroleum resins derived from unsaturated aliphatic and aromatic hydrocarbons.

More particularly this invention relates to resins comprising block copolymers which are particularly effective when combined with elastomer block copolymers as tackifiers for hot melt pressure sensitive adhesives.

U.S. Pat. No. 3,950,453 describes a process for preparing petroleum resins said to be compatible with ethylene-vinyl acetate copolymers for use in hot melt adhesives. This process involves first polymerising C₄ /C₅ conjugated diolefins with at least one C₄ to C₁₀ monolefinic unsaturated hydrocarbon as a first feed portion and secondly polymerising said conjugated diolefins as a second feed portion, the first and second polymerisations being conducted in the presence of a Friedel-Crafts catalyst. The proportion of monolefins in the first feed portion should not be higher than 80 wt. %.

U.S. Pat. No. 2,317,857 discloses a process for preparing a resin suitable for moulding or coating by polymerising styrene with isoprene which has been previously partially polymerised catalytically with the aid of an acid-acting metallic halide catalyst such as a BF₃ -ethyl ether complex. U.S. Pat. Nos. 2,317,858 and 2,317,859 relate to copolymers similarly prepared but using respectively butadiene and piperylene instead of isoprene.

As used herein, the hyphen format for the description of hydrocarbon streams such as "C₈ --", "C₉ --", and "C₅ --" indicates "approximately" as the skilled artisan will readily recognize the described feeds to be of the type found from steam cracked naphthas. For example, feed A below, typically contains unsaturated aromatic C₈ and C₉ hydrocarbons. Feed B is recognized as the unsaturated aliphatic-type hydrocarbons also available from steam cracking and including typically the types of components given herein. When the hyphen is used in conjunction with temperatures and where a plus symbol is not used with the degrees indicated, the hyphen before such numbers indicates "about" or "approximately".

In accordance with this invention resins particularly effective for use in tackifiers for hot melt pressure sensitive adhesives and in tackifiers for solvent-based pressure sensitive adhesives are prepared by a process wherein (1) a feed A or a feed B is first polymerised completely and thereafter, either respectively feed B or feed A is added to the reaction mixture and polymerisation continued and the reactor effluent is stripped to obtain the resin. In this process feed A is a C₈ - and/or C₉ -aromatic unsaturated hydrocarbon-containing feed, and feed B is a C₅ -aliphatic unsaturated hydrocarbon-containing feed provided that feed A may contain up to 18 wt. % of C₄ or C₅ unsaturate aliphatic hydrocarbons based on total weight of monomer in feed A.

Feed A i.e the C₈ -and/or C₉ - aromatic unsaturated hydrocarbon-containing feed can be for example styrene, styrene derivatives, petroleum distillates of 100° to 200° C. boiling points which include more than 20 wt. % of styrene and/or styrene derivatives.

One commercially available feed containing C₈ and C₉ aromatic unsaturated hydrocarbons comprises about 10 wt. % styrene, about 1.3 wt. % alpha-methyl styrene, about 11 wt. % meta vinyl toluene, about 4 wt. % para vinyl toluene, about 13 wt. % indene, about 1 wt. % di-methyl styrene about 0.5 wt. % 1-methyl indene, the remainder being mainly non-olefinic aromatic hydrocarbons.

Feed B i.e. the C₅ -aliphatic unsaturated hydrocarbon-containing feed is typically a C₅ distillate in the range of -20° to 100° C. boiling points excluding cyclopentadienes, e.g. piperylene, isoprene, butadiene, hexadiene etc.

Feed A especially when polymerised first, may contain up to 18 wt. % e.g. up to 15 wt. % of C₄ or C₅ unsaturated aliphatic hydrocarbons (based on total weight of monomers in feed) such as those described above in connection with feed B. This proportion of C₄ or C₅ hydrocarbon is preferably from 2 to 10 wt. % based on the total weight of monomers in feed A.

Each feed is preferably dissolved in a diluent and such diluents may be for example aromatic hydrocarbons such as benzene, xylene, toluene; aliphatic hydrocarbons such as heptane, pentane, hexane; naphtha distillates: or halogenated hydrocarbons such as chlorobenzene.

The amount of diluent is preferably 20 to 1000 parts by weight per 100 parts by weight of monomer, more preferably 50 to 500 parts by weight per 100 parts by weight of monomer.

The polymerisations should take place in the presence of a Friedel-Crafts catalyst.

Suitable Friedel-Crafts catalysts include aluminium chloride, aluminium bromide, aluminium chloride/hydrochloric acid/aromatic hydrocarbon complex or aluminium chloride/ alkyl halide/aromatic hydrocarbon complex. In the former complex the aromatic hydrocarbon is preferably an alkylated hydrocarbon, e.g. O-xylene, mesitylene, ethyl benzene or isoproyl benzene and in the latter complex the alkyl chain of the alkyl halide can be linear or branched and can vary from 1 to 30 carbon atoms.

Other suitable Friedel-Crafts catalysts are acid liquid AlCl₃ sludges obtained as by-products during the alkylation of benzene or any other substituted aromatics (e.g. toluene or xylene) with branched chain olefins.

Apart from aluminium trichloride, the preferred Friedel-Crafts catalyst is boron fluoride gas or a complex of BF₃ with aromatic compounds such as phenol.

Generally, from 0.1 to 5 wt. %, e.g. 0.2 to 1.5 wt. % of Friedel-Crafts catalyst based on the total weight of monomers is used.

In the first polymerisation the reaction temperature is preferably 0° to 100° C., more preferably 20° to 70° C. and the reaction pressure may be atmospheric or higher or lower than atmospheric.

In order to avoid the production of large quantities of C₅ /aromatic random copolymers in the second polymerisation step which would produce a resin having poor pressure sensitive adhesion properties it is necessary for the residence time to be sufficient for complete polymerisation of feed A or feed B in the first polymerisation step. In practice a reaction time of several minutes to 12 hours, preferably 0.2 to 3 hours is usually necessary.

In the second polymerisation suitable and preferred reaction temperature, reaction pressure and reaction time are similar to those given above in connection with the first polymerisation. Usually it is not necessary to add any further catalyst but nevertheless further catalyst may be added to the second reactor if desired.

After the second polymerisation has been completed the reaction effluent should be neutralised so as to kill and eliminate the catalyst. This may be achieved by washing with aqueous solution of alkali, ammonia or sodium carbonate, or by the addition of an alcohol such as methanol and subsequent filtration.

After neutralisation the effluent should be stripped of unreacted hydrocarbons by steam stripping or vacuum distillation. This may be carried out at ambient temperature to 250° C. under an inert gas such as nitrogen gas, at atmospheric pressure. The desired resin is obtained by steam-distilling the stripped effluent e.g. at 250° C.

Usually the resin obtained has an average molecular weight (GPC method) of 500 to 2000, a softening point (JIS K-2531) of 70 to 120° C. The aromatic component in the resin may be 3 to 70 wt. %, preferably 5 to 50 wt. %.

The resins obtained can be used in many applications which require low viscosity, good flexibility and elongation before or especially after chemical modification with polar compounds such as phenols, unsaturated anhydrides such as maleic anhydride or unsaturated acids (e.g. fumaric acid). These resins are designed for a wide range of end uses and applications. They can be applied to paper, metal, thermoplastic films, Cellphane (Registered Trade Mark), polyester, PVC, woven or non woven fabrics, glass etc. and for bonding such materials together. Typical applications are hot melts, carpet backing, coating with drying oil formulations, book binding, paper sizing or in any applications involving natural or synthetic and/or rubbers such as caulks, sealants or rubber tackification.

More especially they may be used as tackifiers with natural rubber or synthetic, diene-containing rubbers such as polyisoproprene, EPDM, butyl, chlorobutyl, bromobutyl, neoprene and block copolymers for example styrene/isoprene rubber (Shell Cariflex (Registered Trade Mark) TR 1107) and mixture of such rubbers. Generally in such a use the resin is mixed with the rubber in amounts from 65 to 250 parts per hundred parts of rubber preferably 100 to 175 parts.

Other applications involving such resin properties are pressure sensitive adhesives, hot melt adhesives, hot melt pressure sensitive adhesives, low temperature adhesives, label adhesives, latex adhesives, surgical tapes and making tapes where they may be blended with polymers such as ethylene/vinyl acetate copolymers and optionally with wax.

According to this invention one can use as a component in an adhesive formulation the resin prepared by the above described process.

Thus the present invention can also provide a hot melt adhesive comprising

(i) an ethylene vinyl acetate copolymer, preferably 20 to 30 wt. %

(ii) wax, preferably 40 to 60 wt. %, and

(iii) a resin, preferably in a proportion of 20 to 30 wt. %, said resin being prepared by the above described process.

In the Figure the process of reacting the two monomers in the two separate reactors followed by inhibition of the catalyst in the receiver is schematically shown.

In the preferred manner of carrying out the process of the invention the C₈ - and/or C₉ aromatic unsaturated hydrocarbon containing feed and catalyst are fed into the first reactor and polymerised on a continuous basis. The reactor effluent which includes live catalyst is continuously sent to the second reactor where C₅ -aliphatic unsaturated hydrocarbon-containing feed is also fed. A mixture of the effluent and the aliphatic components are continuously polymerized in the second reactor. The order of monomer polymerisation can however be changed, i.e. aliphatic monomer polymerisation at the first reactor and aromatic monomer polymerisation at the second reactor.

In the process of aromatic monomer polymerisation, up to 15 wt. % of aliphatic monomer can be added to obtain C₅ /C₉ random copolymer which gives better compatibility with block copolymers. After finishing the polymerisation at the second reactor, the reactor effluent from the second reactor is sent to the neutralization section where the catalyst is killed and eliminated. After that, the effluent is steam-stripped and the resin of the invention is obtained.

EXAMPLE

In this Example the reactions were performed in the manner shown in the Figure as as described above. The specific reaction conditions etc. were indicated below:

    ______________________________________                                         For Run 1                                                                      ______________________________________                                         (i) polymerization of the 1st reactor                                          Reactor size:  1 l                                                             Raw material components:                                                                      styrene 40 wt. %                                                               steam cracked                                                                  naphtha 60 wt. %                                                               (total through-                                                                put 400 ml/hr)                                                  Catalyst:      AlCl.sub.3 1.0 wt. % per total feeds                            Reaction temperature:                                                                         50° C.                                                   Average residence                                                                             35 minutes                                                      time:                                                                          (ii) Polymerisation of the 2nd reactor                                         Reactor size:  1 l                                                             Added raw materials:                                                                          C.sub.5 distillates including                                                  34 wt. % piperylene                                                            (500 ml/hr)                                                     Reaction temperature:                                                                         70° C.                                                   Average residence                                                                             63 minutes                                                      time at reactor:                                                               (iii) catalyst is decomposed in aqueous ammonia. The                           catalyst residue was eliminated by a centrifugal                               separation method. Afterwards the effluent was                                 stripped at room temperature 250° C. under nitrogen                     gas. The resin of the invention was obtained by                                steam distillation.                                                            ______________________________________                                    

This reaction was repeated in Run 2 with different feeds A and B as shown in Table 1.

The properties of the two resins obtained are also shown in Table 1.

                  TABLE 1                                                          ______________________________________                                                        Run 1     Run 2                                                                1st   2nd     1st     2nd                                       ______________________________________                                         Feed Components                                                                Piperylene-rich C.sub.5                                                                         --      100     15    100                                     Styrene          40      --      35    --                                      SCN.sup.(1)      60      --      50    --                                      Feed Rate ml/h)  400     500     400   500                                     Reaction Temperature(°C.)                                                                50       70     50     70                                     Resin Properties                                                               Sp.Gr. (25/4° C.)                                                                        1.01        1.01                                              Softening Point (°C.)                                                                    84.6        79.6                                              Colour Gardner   70          5.5                                               WCP (40/20/40).sup.(2)                                                                          70(--)      70(--)                                            Styrene content  36          40                                                Mn               687         730                                               Mw               1795        1839                                              Mw/Mn            2.61        2.51                                              ______________________________________                                          .sup.(1) Steam cracked naphtha                                                 .sup.(2) Wax cloud point of a blend of 40 wt. % wax, 20 wt. % resin and 4      wt. % of ethylenevinyl acetate copolymer.                                

The pressure-sensitive adhesive (PSA) properties of the two resins obtained in runs 1 and 2 were determined and the results shown in Table 2 which also compares them with prior art resins.

Details of the tests were as follows:

    ______________________________________                                         PSA Performance Measurement                                                    ______________________________________                                         SIS elastomer:                                                                              Cariflex TR-1107 (Shell Chemicals)                                Plasticizer: Esso process oil 765N                                                          (aromatic 9%; napahthalene 33%                                                 remainder paraffin)                                                            Esso process oil L2                                                            (aromatic 20%, naphthalene 33%                                                 remainder paraffin)                                               Resins compared:                                                                            Aliphatic type: Escorez 1310                                                   Aromatic type                                                     Tape preparation:                                                                           Adhesives consisting of SIS (100)/resin                                        (100)/oil(20) are coated on to Kraft                                           paper.                                                            ______________________________________                                    

It can be seen that in general the resins prepared by the process of the invention (Tests 1 and 4) and blends of them with C₅ resin (E1310) (Tests 2,3,5 and 6) had properties superior to those of prior art resins (Tests 7, 8 and 9).

                                      TABLE 2                                      __________________________________________________________________________     PSA Performance                                                                                   Tests                   Comparison Tests                                       1   2   3   4   5   6   7  8  9                             __________________________________________________________________________     Run 1 Resin        100 75  50                                                  Run 2 Resin                    100 75  50                                      C.sub.5 Resin (Escorez E1310)                                                                         25  50      75  50  100   60                            Aromatic resin 100% styrene                   100                                                                               40                            Cariflex - 1107    100 100 100 100 100 100 100                                                                               100                                                                               100                           Plasticiser (Oil)  20  20  20  20  20  20  20 20 20                            PSA Performance                                                                180° Peel Strength (g/25 mm)                                                           25° C.                                                                      1610                                                                               1310                                                                               1140                                                                               1430                                                                               1400                                                                               1610                                                                               1280                                                                              1290                                                                              1190                          J Dow Ball Tack (No)                                                                          25° C.                                                                      24  26  24  24  26  25  23 16 21                            Cohesion (min) 25° C.                                                                      >360                                                                               >360                                                                               >360                                                                               270 180 >360                                                                               110                                                                               0  0                             Shear Adhesion (min)                                                                          25° C.                                                                      >360                                                                               360 300 >360                                                                               >360                                                                               300 40 350                                                                               260                           __________________________________________________________________________

COMPARATIVE EXAMPLE

To compare the properties of the resins prepared by the process of this invention, i.e. two step polymerisation, with resins prepared by one step polymerisation a feed of C₅ distillates and styrene in which the styrene content was 44 wt. % was polymerised using an AlCl₃ catalyst.

The PSA properties obtained were as follows:

    ______________________________________                                         180° C. Peel Strength at 25° C. (1)                                                     1300   g/25 mm                                          J Dow Ball Tack No at 25° C. (2)                                                               20                                                      Cohesion at 25° C. (3)                                                                         18     min                                              Shear adhesion at 40° C. (4)                                                                   52     min                                              ______________________________________                                          (1) Peel Strength  PSTC No. 1                                                  (2) Ball Tack  J Dow method                                                    (3) Cohesion  PSTC method  (Stainless Steel panel, Kraft paper specimen 2      mm × 25 mm, at room temperature weight 1 Kg)                             (4) Shear adhesion at 40° C.  similar to PSTC cohesion method but       us Kliner cardboard as test panels. Test specimen is Kraft tape 25 mm          × 25 mm. Weight 1 Kg. Measure time until specimens fall down at          40° C.                                                            

It can be readily seen that the resins produced by the process of the invention have superior properties compared with those of a similar resin but prepared in a one step polymerisation process. 

We claim:
 1. An adhesive composition comprising natural rubber, synthetic diene-containing rubber or mixtures thereof and as tackifier therefor from 65 to 250 parts per hundred parts of rubber of a block copolymer tackifier resin from a reaction mixture wherein a feed A or feed B is polymerized completely in the presence of a Friedel-Crafts catalyst and thereafter either respectively feed B or feed A is added to the reaction mixture and polymerization continued and the reactor effluent is stripped to obtain the resin, said feed A being a feed of about C₈ or C₉ aromatic unsaturated hydrocarbon-containing feed, and feed B being a feed of about C₅ aliphatic unsaturated hydrocarbon-containing feed, provided that feed A may contain up to 18 wt. % of C₄ or C₅ unsaturated aliphatic hydrocarbons based on the total weight of monomers in feed A.
 2. An adhesive composition according to claim 1 wherein resin feed A comprises about 10 wt. % styrene, about 1.3 wt. % alpha methyl styrene, about 11 wt. % meta vinyl toluene, about 4 wt. % para vinyl toluene, about 13 wt. % indene, about 1 wt. % di-methyl styrene, about 0.5 wt. % 1-methyl styrene, and the balance mainly non-olefinic aromatic hydrocarbons.
 3. An adhesive composition according to claim 1 wherein resin feed B comprises a C₅ distillate in the range of about 20° to 100° C. boiling points.
 4. An adhesive composition according to claim 1 wherein resin feed A contains up to 15 wt. % of C₄ or C₅ unsaturated aliphatic hydrocarbons.
 5. An adhesive composition according to claim 1 wherein the resin has an average molecular weight of 500 to 2,000, a softening point of 70° to 120° C., and an aromatic content of 3 to 70 wt. %.
 6. An adhesive composition of claim 1 wherein said rubber is a synthetic rubber selected from the group consisting of polyisoprene, EPDM, butyl, chlorobutyl, bromobutyl, neoprene, block copolymers, and mixtures thereof.
 7. An adhesive composition of claim 1 wherein said resin is present in an amount from 100 to 175 parts per hundred parts of rubber.
 8. An adhesive composition of claim 6 wherein said synthetic rubber is a styrene/isoprene block copolymer. 